1AC_055_2000 © 2000, Cisco Systems, Inc. Fast IP Routing Axel Clauberg Consulting Engineer Cisco...
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Transcript of 1AC_055_2000 © 2000, Cisco Systems, Inc. Fast IP Routing Axel Clauberg Consulting Engineer Cisco...
1AC_055_2000 © 2000, Cisco Systems, Inc.
Fast IP RoutingFast IP Routing
Axel ClaubergConsulting Engineer
Cisco Systems [email protected]
Axel ClaubergConsulting Engineer
Cisco Systems [email protected]
2AC_055_2000 © 2000, Cisco Systems, Inc.
AgendaAgenda
• The Evolution of IP Routing
• Transmission Update: 10GE
• Router Architectures
• So, it‘s all just speed ?
3AC_055_2000 © 2000, Cisco Systems, Inc.
The Evolution of IP RoutingThe Evolution of IP Routing
4AC_055_2000 © 2000, Cisco Systems, Inc.
Heard around the corner ?Heard around the corner ?
• IP Routers are slow, sw-based
• IP Routers cause high latency
• IP Routers are undeterministic
• IP Routers do not support QoS
5AC_055_2000 © 2000, Cisco Systems, Inc.
WAN Customer Access Speed WAN Customer Access Speed EvolutionEvolution
• Late 1980s: 9.6 Kb/s .. 64 Kb/s
• Early 1990s: 64 Kb/s .. 2 Mb/s
• Late 1990s: 2 Mb/s .. 155 Mb/s
• Early 2000s: 155 Mb/s .. 10 Gb/s
6AC_055_2000 © 2000, Cisco Systems, Inc.
Backbone EvolutionBackbone Evolution
• Late 1980s: 56/64 Kb/s
• Early 1990s: 1.5/2 Mb/s
• Mid 1990s: 34 Mb/s, 155 Mb/s
• Late 1990s: 622 Mb/s, 2,5 Gb/s
• Early 2000s: 10 Gb/s, 40 Gb/s
• Late 1980s: 10 Mb/s
• Early 1990s: 100 Mb/s (FDDI)
• Mid 1990s: 155 Mb/s (ATM)
• Late 1990s: nx FE, 155 Mb/s, 622 Mb/s, GE
• Early 2000s: 10 Gb/s, n x 10 Gb/s
WAN Campus
7AC_055_2000 © 2000, Cisco Systems, Inc.
Transmission Update: 10GETransmission Update: 10GE
8AC_055_2000 © 2000, Cisco Systems, Inc.
Lower Cost and OverheadLower Cost and OverheadLower Cost and OverheadLower Cost and Overhead
MAN/WAN IP Transport MAN/WAN IP Transport Alternatives Alternatives
IPIP
ATMATM
OpticalOptical
B-ISDN
IPIP
OpticalOptical
IPIP
SONET/SDHSONET/SDH
OpticalOptical
ATMATM
SONET/SDHSONET/SDH
IPIP
OpticalOptical
Multiplexing, Protection and Management at every LayerMultiplexing, Protection and Management at every Layer
IP over ATM
IP over SDH IP over Optical
IPIP
EthernetEthernet
OpticalOptical
IP over Ethernet
GE
10GE
9AC_055_2000 © 2000, Cisco Systems, Inc.
Ethernet Scaling HistoryEthernet Scaling History
• 1981: Shared 10 Mbit 1x
• 1992: Switched 10 Mbit 10x
• 1995: Switched 100 Mbit 100X
• 1998: Switched 1 Gigabit 1000X
• 200x: Switched 10 Gigabit 10000X
10AC_055_2000 © 2000, Cisco Systems, Inc.
Moving the Decimal Point: 10 GbE PerformanceMoving the Decimal Point: 10 GbE Performanceand Scalabilityand Scalability
1996 1997 1998 1999 2000
1 Gbps
100 Mbps
10 Gbps 10 GbpsEthernet
Gigabit Ethernet
Fast Ethernet
Fast EtherChannel
Gigabit EtherChannel
STM-64
2001 2002
10 GbE IEEE 10 GbE IEEE 802.3ae 802.3ae StandardStandard
• LAN applications
• Metro applications
• WAN applications
11AC_055_2000 © 2000, Cisco Systems, Inc.
Why 10 Gigabit EthernetWhy 10 Gigabit Ethernet
• Aggregates Gigabit Ethernet segments
• Scales Enterprise and Service Provider LAN backbones
• Leverages installed base of 250 million Ethernet switch ports
• Supports all services (packetized voice and video, data)
• Supports metropolitan and wide area networks
• Faster and simpler than other alternatives
12AC_055_2000 © 2000, Cisco Systems, Inc.
IEEE Goals for 10 GbEIEEE Goals for 10 GbE(Partial List) (Partial List)
• Preserve 802.3 Ethernet frame format
• Preserve minimum and maximum frame size of current 802.3 Ethernet
• Support only full duplex operation
• Support 10,000 Mbps at MAC interface
• Define two families of PHYs
LAN PHY operating at 10 Gbps
Optional WAN PHY operating at a data rate compatible with the payload rate of OC-192c/SDH VC-4-64c
13AC_055_2000 © 2000, Cisco Systems, Inc.
IEEE 802.3ae Task Force MilestonesIEEE 802.3ae Task Force Milestones
19991999 20012001 2002200220002000
PARPARDraftedDrafted
PARPARApprovedApproved
802.3ae802.3aeFormedFormed
First First DraftDraft
WorkingWorkingGroupGroupBallotBallot
LMSCLMSCBallotBallot
StandardStandard
HSSG= Higher Speed Study Group
PAR= project authorization request
802.3ae= the name of the project and the name of the sub-committee of IEEE 802.3 chartered with writing the 10GbE Standard
Working group ballot= task force submits complete draft to larger 802.3 committee for technical review and ballot
LMSC: LAN/MAN Standards Committee ballot. Any member of the superset of 802 committees may vote and comment on draft
HSSGHSSGFormedFormed
First 10GE First 10GE deliveriesdeliveries
14AC_055_2000 © 2000, Cisco Systems, Inc.
10 Gigabit Ethernet Media Goals10 Gigabit Ethernet Media Goals
1300 nm Laser1300 nm LaserCDWM (4x2.5)CDWM (4x2.5)
1300 nm Laser1300 nm Laserstandard reachstandard reach
Media TypeMedia TypeTypeType
1550 nm Laser1550 nm Laserextended reachextended reach
40-100 km 40-100 km std/dispersion free fiberstd/dispersion free fiber
single mode fibersingle mode fiber 2-10 km 2-10 km
multimode fibermultimode fiber 300 m 300 m
200 m 200 m ribbon multimode fiberribbon multimode fiber
Max DistanceMax Distance
780 nm VCSEL780 nm VCSELmultichannelmultichannel
15AC_055_2000 © 2000, Cisco Systems, Inc.
IEEE StatusIEEE Status
• 802.3ae Meeting 10.-14. Juli 2000
• 75% Consensus
1550nm Transceiver 40 Km @ SMF
1300nm Transceiver 10 Km @ SMF
• No Consensus yet
Multimode Support
300m mit 62.5µ 160/500 Mhz*Km MM
50µ 2000/500 MHz*Km MM
16AC_055_2000 © 2000, Cisco Systems, Inc.
Router ArchitecturesRouter Architectures
17AC_055_2000 © 2000, Cisco Systems, Inc.
ComponentsComponents
• Memory Architecture
• Interconnect
• Forwarding Engine
• Scalability
• Stability
• Queueing / QoS
18AC_055_2000 © 2000, Cisco Systems, Inc.
Basic DesignBasic Design
• Data are of random sizes
• Arrival is async, unpredictable, independantly on i/f
• Data have to be buffered
• TCP/IP traffic is bursty, but short-term congestion only
Router... ...Inputs Outputs
ForwardingEngine
RouteProcessor
BufferMemory
Interfaces
19AC_055_2000 © 2000, Cisco Systems, Inc.
How much buffers ?How much buffers ?
• Rule of Thumb: RTT x BW(Villamizer & Song, High Performance TCP in ANSNET,
1994)
• STM-16 @ 200 ms: ~ 60 MB buffering capacity
20AC_055_2000 © 2000, Cisco Systems, Inc.
How to Buffer ?How to Buffer ?
• SRAM
Fast, Power-hungry, Density 8 Mb -> 16 Mb, Simple Controller Design
• DRAM / SDRAM
Slower, Less Power, Density 64 Mb -> 256 Mb, Complex Controller Design
21AC_055_2000 © 2000, Cisco Systems, Inc.
InterconnectInterconnect
• Switch Fabric / Crossbar
• Shared Memory
• Variations
22AC_055_2000 © 2000, Cisco Systems, Inc.
Switch Fabric / CrossbarSwitch Fabric / Crossbar
• Packet forwarding decision done on each linecard
• Ingress and Egress Buffering on Linecards
• Possible Problem: Head of Line Blocking
• Solution: VOQ
LineCard 0Line
Card 0
SwitchFabricSwitchFabric
SchedulerScheduler
LineCard 1Line
Card 1
LineCard N
LineCard N
LineCard 0Line
Card 0
LineCard 1Line
Card 1
LineCard N
LineCard N
RPRP RPRP
Ingress Line Cards Egress Line Cards
23AC_055_2000 © 2000, Cisco Systems, Inc.
Linecard in DetailLinecard in Detail
Physical Layer
(Optics)
Physical Layer
(Optics)
Layer 3 Engine
Layer 3 Engine
Fabric InterfaceFabric
Interface
RXRX
TXTX
CPUCPU
To FabricTo Fabric
From FabricFrom Fabric
SwitchFabricSwitchFabric
SchedulerScheduler
• HOL Blocking can occur when packet cannot flow off transmit linecard• Packet will be buffered on receiving linecard• Packet blocks other packets to other linecards• Solution: Virtual Output Queues, one per egress linecard
24AC_055_2000 © 2000, Cisco Systems, Inc.
Receive Line CardTransmitLine Card
Group of 8 CoS Queues Per Interface (M-DRR)
InputPorts
OutputPorts
Cro
ssb
ar S
wit
ch F
abri
cW-RED
CAR
CEF
VirtualOutputQueues
DRR
GSR Queuing ArchitectureGSR Queuing Architecture
25AC_055_2000 © 2000, Cisco Systems, Inc.
Shared Memory ArchitectureShared Memory ArchitecturePhysically CentralizedPhysically Centralized
• One large memory system, data passing through it
• Simple memory management
• High speed memory
• Simple Linecards
• Needs SRAM for high speeds
Interconnects&
ForwardingEngine
Interconnects&
ForwardingEngine
2.5Gbps
2.5Gbps
2.5Gbps
2.5Gbps
Line Cards 1-8
Mem
ory
Con
trol
ler
40G
26AC_055_2000 © 2000, Cisco Systems, Inc.
Shared Memory ArchitectureShared Memory ArchitectureDistributedDistributed
• Memory distributed over linecards
• Memory controller treats sum of pieces as shared memory
• Packet forwarding decision in central engine(s)
• Difficult to maximize interconnect efficiency
Egress line cards simply request packets from shared memory
Causes Head of Line (HOL) blocking and high latency, worsening under moderate-to-heavy system load or with multicast traffic
MemoryController
& ForwardingEngine(s)
MemoryController
& ForwardingEngine(s)
MemorySystem
2.5Gbps
2.5Gbps
MemorySystem
2.5Gbps
2.5Gbps
Line Cards 1-8
27AC_055_2000 © 2000, Cisco Systems, Inc.
Switch Fabric vs. Shared MemorySwitch Fabric vs. Shared Memory
• Shared Memory requires only half the buffer space
• HOL Blocking in Shared Memory, especially for Multicast
• Involvement of distributed shared memory causes more points of failure
28AC_055_2000 © 2000, Cisco Systems, Inc.
Forwarding EngineForwarding Engine
• Classifying the packet
IPv4, IPv6, MPLS, ...
• Packet validity (TTL, length, ...)
• Next Hop
• Basic Statistics
• Optional:
• Policing, Extended Statistics, RPF check (security, Multicast), QoS, Tunnel, ...
• Distributed vs. Central
29AC_055_2000 © 2000, Cisco Systems, Inc.
Central Forwarding ?Central Forwarding ?
• IP Longest match
Hash vs. TCAM vs. Tree Lookup
• Tree Lookup requires high number of routing table lookups
Need SRAM
Danger to run out of SRAM
Forwarding speed dependant on depth of routing table
30AC_055_2000 © 2000, Cisco Systems, Inc.
Distributed ForwardingDistributed Forwarding
• One copy of forwarding info per linecard
• Parallel processing without sync or communication between linecards
• Able to use TCAMs and SDRAMs
31AC_055_2000 © 2000, Cisco Systems, Inc.
So, it’s all just speed ?So, it’s all just speed ?
32AC_055_2000 © 2000, Cisco Systems, Inc.
So, it’s just So, it’s just speed ?speed ?
• Services
IP Multicast
IP QoS
Security
• IPv6
• MPLS
• Manageability
• Availability
• Investment protection
33AC_055_2000 © 2000, Cisco Systems, Inc.
Interdomain MulticastInterdomain MulticastCampus MulticastCampus Multicast
Multicast SolutionsMulticast SolutionsEnd-to-End ArchitectureEnd-to-End Architecture
• End Stations (hosts-to-routers):IGMP
• Switches (Layer 2 Optimization):IGMP Snooping
• Routers (Multicast Forwarding Protocol):
PIM Sparse Mode
• Multicast routing across domainsMBGP
• Multicast Source DiscoveryMSDP with PIM-SM
ISP B
Multicast SourceY
ISP A
Multicast SourceX
ISP B
DRRP
RP
DRDRIGMP PIM-SM
CGMPMBGP
MSDP
ISP A
34AC_055_2000 © 2000, Cisco Systems, Inc.
SummarySummary
• IP Routers have evolved during the past years
• Line rate up to 10 Gb/s
• Crossbar architectures with distributed forwarding seem to scale better than shared memory architectures
• Services remain the most decisive factor
35AC_055_2000 © 2000, Cisco Systems, Inc.
OutlookOutlook
• 10 Gb/s Interfaces supported in 2000
10GE, STM-64/OC-192
• High density of 10 Gb/s interfaces soon in a PoP
• Next step will be STM-256/OC-768 = 40 Gb/s
• Will these routers be „Palm-Size“ ?
Probably not...
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